Power MOSFETS are a type of Metal Oxide Semiconductor Field Effect Transistor (MOSFET) that are designed to handle significant power levels. Some of these devices are designed to switch high currents and thus can have low on resistance. Some of these devices are designed to tolerate high voltages across the device's terminals. The voltage tolerance and current requirements have resulted in device configurations different from tradition MOSFET designs. One such device configuration involves trenches, which have been used to provide vertical channel conduction for such power MOSFETS. Orienting these MOSFETS vertically has improved the layout efficiency of such devices.
Bonding pads are used to facilitate electrical connection between a semiconductor device and other circuit components. Bonding pads provide a large surface areas of a metal to which a wire can be bonded. Wire bonding machines can bond wires between leads of a package and bonding pads of a semiconductor chip. These wire bonds provide electrical communication between the semiconductor chip and the package leads. In some embodiments solder bumps are formed on the bonding pads. The solder bumped chip can then be flipped and aligned onto a circuit board that has pads that are complementary to and align with the bumped pads of the flipped semiconductor chip. After aligning the flipped semiconductor chip with the complementary pads of the circuit board, the solder can be heated so as to make it to reflow. After reflow of the solder bumps, the solder bumps provide electrical connectivity between the bonding pads of the semiconductor chip and the complementary pads of the circuit board.
Because bonding pads occupy large surface areas of the chip, they can present large parasitic capacitances between the metal of the bonding pad and a top surface of the semiconductor directly beneath the bonding pads. Large parasitic capacitances can capacitively communicate large voltage transients between the bonding pads and the top surface of the semiconductor. Capacitive communication between a bonding pad and the top surface of the semiconductor can be further facilitated by large voltage transients on either or both plates of such parasitic capacitors. Switching high voltages can produce such large voltage transients.